Effect of Coupling Agents and Weathering on the Mechanical Properties of Wood‐Polymer Composites

Abstract

Polyvinylchloride (PVC), polypropylene (PP), and low density polyethylene (LDPE)were used to prepare a range of wood-polymer blends containing 20, 40, and 60% w/w medium density fibreboard sawdust (90-150 microns and 212-850 microns In trod u c tionWood-polymer composites are a fascinating area in both polymers and wood, which arose due to a desire to recycle plastic and wood dust. When using the composites for outdoor applications it is necessary to balance the physical properties against water up-take. A wood-polymer composite with a high MFI polymer enhances properties but increases water up-take, whereas a low MFI polymer has reduced mechanical performance but an increased resistance to water up-take [ 11. Wood-filled polyethylene exhbits a greater degree of creep strain in freshwater than in air or saltwater [2]. Polyethylene-based wood composites reportedly offer a hgher degree of heat resistance with a heat distortion temperature of about 82OC at 264 psi, and they may also be somewhat less expensive than PVC formulations. The key advantage of PVC-based wood composites is their stainability or paintability. Little, if any, treatment is required for the stain or paint to adhere to the PVC-composite. It was found that for both cellular and solid PVC-composites, the moisture content should be kept in the 0.5-1% range. PVC-wood composites offer many advantages over conventional lumber. However, one of the major disadvantages is the increased density [3]. Other studies have used compatibilisers such as maleic anhydride and various processing aids to improve the mechanical properties and the water up-take of wood-polymer composites [4-61.When wood is compounded w i t h a polymer, the wood acts as a filler decreasing the mechanical properties. At high wood loadings there exists a non-continuous layer of polymer on the composite surface, and the associated disadvantage is water being absorbed into the matrix further decreasing the properties. Coupling agents are used in an attempt to convert wood filler into a reinforcing agent by creating chemical bonds between the wood surface and the polymer chains. Two commonly used coupling agents are maleic anhydride and titanates which are used to increase the composites mechanical properties. Coupling agents are molecular bridges at the interface between two substrates. Titanium-derived coupling agents are unique in that their reaction with the free protons in the inorganic interface results in the formation of organic monomolecular layers on the inorganic surface. Typically, titanate-treated inorganics are hydrophobic, organophilic and organofunctional. When incorporated into polymer systems they often have several effects, such as: promote adhesion; catalyse; improve dispersion and rheology; improve impact strength; do not create embrittlement; improve mechanical properties, and inhibit corrosion [7]. Titanates are able to crosslink or cure a variety of polymers such as polyolefin's, polystyrene, etc. During extrusion the effect of the titanate coupling agent is perman...

Utilization of renewable filler from lichen in low density polyethylene

“…Melt flow index values increased from 2 g 10 min −1 for neat polyethylene to 2.2 g 10 min −1 , indicating a decrease in processability as seen in Table . Meanwhile, a decrease in MFI values can be observed with an increase in filler amount and processability became more feasible . On the other hand, there has not been any change in vicat softening point…”

Effects of titanate coupling agent on the mechanical, thermal, and morphological properties of poly(methyl methacrylate)/hydroxyapatite denture base composites

“…Several methods have been developed to improve the interfacial interactions between inorganic filler and organic polymer matrix, for example, modification by coupling agent, 13 – 17 addition of maleic anhydride compatibilizer, 18 and graft copolymerization. 19 The treatment of polybutadiene rubber/clay and nylon 6/mica using titanate coupling agent demonstrated better mechanical properties, attributed to better adhesion between the matrix and filler.…”

Experimental investigation on mechanical properties of extruded foamed PVC‐wood composites reinforced with continuous glass fibers

“…Compared with WPCs based on PE and PP, PVC‐based WPCs are more durable and exhibit better printability, higher resistance to fire, chemicals, UV, and acceptable mechanical performance. PVC‐wood composites have shown a higher market growth as compared to PE and PP ones over the last decade, and a higher growth rate is also expected over the future years .…”